The present invention relates to data communication, and more particularly to communication between peer-to-peer devices coupled to a system.
Most computer systems are formed of components coupled together using one or more buses, which are used to transmit information between the various system components. Present bus standards such as the Peripheral Component Interconnect (PCI) Specification, Rev. 2.1 (published Jun. 1, 1995) provide a multi-drop bus in which multiple devices may be coupled to the same bus. Accordingly, it is easy to read or write to devices on the same bus.
However, as bus interface speeds increase, bus architectures are moving away from multi-drop architectures towards point-to-point architectures. In such point-to-point architectures, peer-to-peer communication becomes more difficult, as synchronization, ordering, and coherency of such communications becomes more difficult.
Furthermore, such point-to-point architectures may include components using different communication protocols, such that communication between these different components is also difficult. For example, peer-to-peer communication between input/output (I/O) devices may be sent according to a first protocol, but due to the point-to-point architecture and protocols used by other components between the I/O devices, such communication becomes difficult. Typically, such a transaction may be translated from the first bus protocol into equivalent commands of a second (i.e., non-native) bus protocol and forwarded through to the desired target peer device. However, such operations may cause a significant loss of information, including header information of the first bus protocol. Such information loss may negatively affect performance and reliability, such as a system error recovery/debug. Thus a need exists to better transfer data transactions between peer devices, particularly where the transactions pass through a fabric non-native to the peer devices.